This invention relates to preventives and remedies for autoimmune demyelinating diseases which contain an apoptosis-suppressing substance as their effective component.
Fas is a cell surface protein which transmits apoptosis signal to the cell, and Fas is recognized by Fas antibody (Yonehara, S. et al., J. Exp. Med., vol. 169, 1747-1756, 1989) which is a monoclonal antibody produced by immunizing a mouse with human fibroblast. Fas gene was cloned by Itoh, N. et al., and it was then found out that Fas is a cell membrane protein of about 45 kD, and from the amino acid sequence, it was revealed that Fas is a member of TNF receptor family (Cell, vol. 66, pages 233-243, 1991). Mouse Fas gene was also cloned , and the expression of Fas mRNA in thymus, liver, lung, heart, and ovary was confirmed (Watanabe-Fukunaga, R. et al., J. Immunol., vol. 148, pages 1274-1279, 1992).
Human Fas ligand is a polypeptide which has been reported by Nagata et al. to be a native molecule which induces apoptosis of Fas-expressing cells (Takahashi, T. et al., International Immunology, vol. 6, pages 1567-1574, 1994). Human Fas ligand is a glycosilated type II membrane protein of TNF family with a molecular weight of about 40 kD. As in the case of TNF, human Fas ligand in the human body is estimated to be in the form of a trimer (Tanaka, M. et. al., EMBO Journal, vol. 14, pages 1129-1135, 1995). The extracellular domain of the human Fas ligand is highly homologous with the extracellular domain of rat Fas ligand (Suda, T. et al., Cell, vol. 75, pages 1169-1178, 1993) and mouse Fas ligand (Takahashi, T. et al., Cell, vol. 76, pages 969-976, 1994). The human Fas ligand recognizes not only the human Fas but also the mouse Fas to induce the apoptosis, and vice versa, the rat Fas ligand and the mouse Fas ligand also recognize the human Fas to induce the apoptosis.
Considerable researches have also been done on the mechanism of signal transduction in the cell upon the Fas-mediated apoptosis, and identification and cloning of the factor which interacts with the intracellular domain of the Fas, in particular, the region called xe2x80x9cdeath domainxe2x80x9d to transmit or block the signal have been reported. Possibility of the involvement of interleukin-1-converting enzyme (ICE)-related thiol proteases in the signal transduction of the Fas-mediated apoptosis has also been indicated.
Relationship of the apoptosis, in particular, the Fas-mediated apoptosis with various diseases and physiological phenomena has been recently indicated. For example, possibility has been indicated for involvement of abnormal Fas-mediated apoptosis in the death of hepatocytes in viral fulminant hepatitis, in some types of autoimmune diseases, and the like.
Possibility of the involvement of the Fas/Fas ligand system in functions other than the apoptosis, for example, in the function of inducing inflammation by acting on neutrophil has also been indicated (Kayagaki, N. et al., Rinshou Meneki (Clinical Immunology), vol. 28, pages 667-675, 1996).
Autoimmune diseases are diseases induced by the attack of autoreactive lymphocytes after responding to an autoantigen, and the disease is associated with various symptoms. The body does not exhibit any excessive immunoreaction when normal, and self-tolerance is the state established in a normal body. However, abnormality in immunomodulation mechanism invites production of antibodies against various components constituting the self and emergence of autoreactive lymphocytes. The autoreactive T cell are normally removed in thymus by apoptosis. However, when such autoreactive T cell transfers to periphery without being removed in thymus by some abnormality, they are accumulated in the periphery. Tolerance is also established for B cells, and autoreactive B cells are normally removed by apoptosis. However, when the autoreactive B cells fail to be removed by some abnormality, they are also accumulated in the periphery as in the case of the T cells. The autoimmune disease are caused by such autoreactive lymphocytes.
Autoimmune demyelinating disease is induced by an autoantibody specific to nerve system, and the disease is associated with selective destruction of the myelin and the cells constituting the myelin. Histologically, the disease is associated with disappearance of myelin, cellular infiltration in the region surrounding the vein. The disease is associated with clinical conditions of loss of sight, paresthesia, quadriplegia, and other neurologic manifestation.
Detailed etiology of the demyelinating disease is not fully found out. For example, for the demyelinating inflammation undergoing recurring remission and relapse such as multiple sclerosis include, possibility of the involvement of viral infection (Carp, R. I. et al., Prog. Med. Viol., vol. 24, pages 158-177, 1978) is indicated in addition to the involvement of autoimmunity (De Keyser, J., Neurology, vol. 38, pages 371-374, 1988).
Typical treatments which has been employed for the demyelinating disease include treatment by nonspecific immunosuppression by the use of an immunosuppressant in combination with ACTH (adrenocorticotropic hormone) (Saida K. Saishin-Igaku (Current Medicine), vol. 10, pages 1963-1971, 1991). This treatment, however, failed to exhibit prolonged effects, and moreover, this treatment is not effective for the disease of chronic, progressive type (Weiner et al., Neurology, vol. 39, pages 1143-1149, 1989). In view of such situation various treatments are currently investigated for specifically suppressing the activity of the autoimmune T cells, including the administration of T cell vaccine (Ben-Nun, A et al., Nature, vol. 292, pages 60-61, 1981) or T cell receptor vaccine (J. Immunol, vol. 152, page 2510, 1994; J. Immunol, vol. 152, page 2520, 1994), oral immunity tolerance (Science, vol. 259, page 1321, 1993), peptide analog (Immunol. Today, vol. 14, page 602-609, 1993), and administration of anti-CD4 antibody. No results with significant effectivity has so far been reported except for some of these agent (T cell receptor vaccination) wherein the effect of reducing the frequency of autoantigen-reactive T cell in the peripheral blood has been reported.
When homogenate of spinal cord is subcutaneously inoculated with Freund""s complete adjuvant containing killed Mycobacterium tuberculosis, symptom of encephalomyelitis such as paralysis of hind legs is evoked in sensitive animals at 10 to 14 days after the inoculation. This is the prototype of the experimental autoimmune encephalomyelitis (EAE). This is also a typical model of autoimmune disease derived by immunizing an experimental animal with a protein antigen or a peptide from brain, and this model has been extensively investigated from old days lip as a disease model of multiple sclerosis and acute disseminated encephalomyelitis (ADEM). Analysis of EAE has brought various findings including the involvement of T cell specific to autoantigens such as myelin basic protein and proteolipid protein expressed in central nerve system (Ota, K. et al., Nature, vol. 396, pages 183-187, 1990).
Various studies have been recently conducted and reported for the relation between the multiple sclerosis and the apoptosis mediated by Fas/Fas ligand system. Sameer, D. et al. reported that they found the Fas ligand expressed in microglia cells and infiltrated T cells and the Fas expressed in oligodendrocytes, in the lesion of human multiple sclerosis (J. Exp. Med., vol. 184, pages 2361-2370, 1996). Kimberly A. et al. (J. Immunol., vol. 159, pages 3096-3099, 1997) and Hanspeter, W. et al. (J. Immunol., vol. 159, pages 3100-3103, 1997) suggested through animal experiment of multiple sclerosis using lpr and gld mouse, which are genetically deficient of the Fas and the Fas ligand, respectively, that the apoptosis mediated by the Fas/Fas ligand is involved in the multiple sclerosis. In the meanwhile, Eileen, A. et al. (J. Clin. Invest., vol. 98, pages 1602-1612, 1996) and Suzana, M. et al. (J. Exp. Med., vol. 186, pages 507-515, 1997) suggested through animal experiment of the multiple sclerosis using the same lpr and gld mouse that the apoptosis mediated by the Fas/Fas ligand is not involved in the multiple sclerosis. In other words, the relationship between the pathology of the multiple sclerosis and the apoptosis mediated by the Fas/Fas ligand system is still unknown and differently conceived depending on the investigator. In addition, efficiency of the drug delivery to brain tissue is generally low, and it is utterly unknown whether the drug which suppresses the apoptosis by the Fas/Fas ligand administered to the body can suppress the Fas/Fas ligand-mediated apoptosis in the brain tissue, and it is also unknown whether the results will be the same as those obtained in the mouse genetically deficient of the Fas or the Fas ligand.
Up until now, there is no preventive and therapeutic agent for autoimmune demyelinating diseases which acts by suppressing the apoptosis, and no therapeutic agent which binds to the Fas ligand has been reported.
An object of the present invention is to provide a preventive and therapeutic agent for autoimmune demyelinating diseases which acts by the novel mechanism of suppressing the apoptosis. More specifically, the present invention provides a preventive and therapeutic agent for autoimmune demyelinating diseases which contains an apoptosis-suppressing substance as its effective component and a therapeutic method wherein such agent is used.
The inventors of the present invention have conducted intensive studies on the relation between the apoptosis and the autoimmune demyelinating diseases in order to save those suffering from such diseases, and found that the pathology is improved in the model of autoimmune demyelinating diseases by the apoptosis-suppressing substance. The present invention has been completed on the bases of such finding.
Accordingly, the present invention is directed to a preventive and therapeutic agent as described below.
(1) A preventive and therapeutic agent for autoimmune demyelinating diseases containing an apoptosis-suppressing substance as its effective component.
(2) A preventive and therapeutic agent according to (1) wherein said apoptosis-suppressing substance is a Fas antagonist.
(3) A preventive and therapeutic agent according to (1) or (2) wherein said apoptosis-suppressing substance is a substance which suppresses Fas-Fas ligand binding.
(4) A preventive and therapeutic agent according to any one of (1) to (3) wherein said apoptosis-suppressing substance is a Fas derivative.
(5) A preventive and therapeutic agent according to any one of (1) to (3) wherein said apoptosis-suppressing substance is an anti-Fas ligand antibody.
(6) A preventive and therapeutic agent according to any one of (1) to (5) wherein said autoimmune demyelinating disease is a disease associated with demyelinating in central nerve system.
(7) A preventive and therapeutic agent according to any one of (1) to (5) wherein said autoimmune demyelinating disease is at least one member selected from acute disseminated encephalomyelitis and multiple sclerosis.
(8) A method for preventing and treating autoimmune demyelinating diseases wherein an apoptosis-suppressing substance is administered.
(9) Use of an apoptosis-suppressing substance in producing a pharmaceutical for preventing and/or treating autoimmune demyelinating diseases.